Opentaxii

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* Ability to enable/disable "huge trees" support in XML parser. Configuration property ``xml_parser_supports_huge_tree`` set to ``yes`` or ``true`` will disable security restrictions and force XML parser to support very deep trees and very long text content.
* Adjust SQL Persistence API implemetation so it works smoothly with MySQL backend.
* Use Python 3.5 instead of Python 3.4 for tests.

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* Minor fixes.
* Dependencies were changed from hard-pinned to more flexible.
* Example of production DB configuration added to docs.

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* Python 3.4 compatibility of the codebase. Tox configuration extended with python 3.4 environment run.
* Flake8 full style compatibility. Flake8 check added to Tox configuration.
* SQLAlchemy session scope issue fixed (related to `38 <https://github.com/EclecticIQ/OpenTAXII/issues/38>`_).
* `opentaxii-delete-blocks` CLI command added (related to `45 <https://github.com/EclecticIQ/OpenTAXII/issues/45>`_).
* `delete_content_blocks` method `added <https://github.com/EclecticIQ/OpenTAXII/commit/dc6fddc27a98e8450c7e05e583b2bfb741f6e197#diff-6814849ac352b2b74132f8fa52e0ec4eR213>`_ to Persistence API.
* Collection's name is `required <https://github.com/EclecticIQ/OpenTAXII/commit/dc6fddc27a98e8450c7e05e583b2bfb741f6e197#diff-ce3f7b939e5c540480ac655aef32c513R116>`_ to be unique in default SQL DB Auth API implementation.

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* Fix for the issue with persistence backend returning ``None`` instead of ``InboxMessage`` object

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* Hard-coded dependencies in ``setup.py`` removed.

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* Versions of dependencies are pinned.
* Code adjusted for a new version of `anyconfig <https://pypi.python.org/pypi/anyconfig>`_ API.
* Test for configuration loading added.